For centuries rollback cans or comeback cans were made as play toys. When rolling on the floor, the can rolls, stops, and returns back by itself along the same path to the same launching destination. The rollback can is made of a round cylinder can with both end lids, a rubber band tied between the centers of both lids, and a weight anchored at the middle of the rubber band and hung above the bottom of the cylinder. Another method of making the rollback can is to use a shaft and a spiral coil spring. The shaft is extended through the centers of the can's lids. A weight is anchored at the center of the shaft. The inner end of the spring is attached to the shaft and the outer end of the spring is attached to the cylinder. When rolling, kinetic energy from the rotating can is transferred to potential energy stored in the rubber band or spring. Once the can stops, the rubber band or spring releases its potential energy rolling the can back along the same path to the same launching destination.
Some manufacturers make the rollback can shape like a ball. The mechanism inside the ball is the same as the mentioned mechanism inside the rollback can. In order for the ball to rolling back, it has to be rolled only in the direction, perpendicular to the rubber band string or shaft, like the rollback can. The ball cannot roll back in other directions.
U.S. patent US 2005/0107192 A1 “Rolling Play Toy” provides a method of varying the center of mass of the ball by adjustable bolt heads from the nuts embedded in the ball. When rolling, the bolt heads move and rotate with the ball in one solid piece. Different positions of bolt heads give different trajectories. However, all of the trajectories that are potentially attainable are curves and not a straight line. Also, most of the trajectories cannot return to the same destination.
There is no prior art similar to my invention that a ball with a novel mechanical tracking device that can return by itself on the same straight line path to the same or approximately the same destination from which it was launched from any angle on a level floor